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Biomedical subjects

W R Dukelow

Publications and source records attributed to W R Dukelow.

At least 19 recordsLinked to original sources
PubMed1999

Incorporation of a GnRH agonist, leuprolide acetate, into regimens with exogenous gonadotropins to produce ovarian stimulation and ovulation in the nonpregnant squirrel monkey.

This study was designed to measure the effects of variations in the length of pretreatment with a GnRH agonist, leuprolide acetate (LA), on subsequent follicular development and ovulation. The hypothesis was that the duration of LA suppression of pituitary function does not adversely affect ovarian response to standardized ovulation induction protocols in squirrel monkeys. The first phase determined the dose and duration of LA needed to achieve a hypogonadal state. One of two groups received daily subcutaneous injections of 50 microg of LA. The other received a single injection of 175 microg of a depot suspension of LA. Sera were assayed for estradiol (E2) and progesterone (P). E2 and P levels increased 2- to 5-fold with peak levels on days 4 and 7, respectively. Suppression of steroid levels took 10 to 15 days in the LA-treated group. Depot-LA did not effectively suppress steroid production. After suppression, females receiving daily LA received five daily injections of hMG to stimulate follicular development. E2 and P increased in these animals. These results suggest that cycling squirrel monkeys have P-secreting capacity throughout the cycle. This may explain how the squirrel monkey is able to accommodate both a short (4-5 day) luteal phase of their 9 day cycle and implantation from 5 to 7 days after ovulation. A second study compared exogenous follicle stimulating hormone (FSH) to endogenous gonadotropins released as a response to LA in ovulation induction. Steroid production and hCG-induced ovulation were assessed. LA treatment was compared to a standard ovulation induction protocol by using a randomized cross-over measures design. There were no differences in E2 and P levels in response to dosages of either LA or hMG. The ovulatory response following LA treatment was not significantly greater than that using FSH. The number of animals with unovulated, large follicles was greater on the FSH protocol (12/18) compared to the LA protocol (3/18). Thus, a single injection of a depot preparation of LA is sufficient to stimulate follicular development and ovulation when followed by an hCG injection. Based on this observation and the data on unovulated large follicles, it is suggested that the ovary responds more readily to endogenous gonadotropins released by LA than to exogenous FSH.

Animals↗
PubMed1997

Cryopreservation of murine zygotes for use in testing culture environments.

Developing one-cell mouse zygotes are more sensitive to in vitro environmental conditions than are cleavage-stage embryos. However, for convenience and reproducibility, cryopreserved two-cell zygotes are routinely used for such assays. Concern over the possibility of inducing damage by exposing one-cell zygotes to cryoprotective agents and freeze-thaw procedures during syngamy led us to examine one-cell zygotes, with and without visible pronuclei, in an effort to minimize or avoid these effects and obtain the highest possible developmental rate. In vivo fertilized mouse zygotes were collected 21 to 43 h after administration of human chorionic gonadotropin (hCG). Suspensions of zygotes in 2M ethylene glycol were aspirated into 0.25-ml plastic insemination straws and slowly cooled at -0.5 degree C/min to -40 degrees C before being plunged into liquid nitrogen for storage. Zygotes were thawed, rinsed, and placed in culture. Zygotes were examined initially for damage from the freeze-thaw procedure. Daily in vitro development was recorded. In this group of zygotes, no damage was apparent immediately after thawing, and a high degree of development in vitro was observed. Thus, usefulness of a cryopreservation method for one-cell murine zygotes has been confirmed.

Animals↗
PubMed1995

In vitro fertilization and the effect of progesterone and 17 alpha-hydroxyprogesterone on acrosome reaction of mouse epididymal spermatozoa.

This study assessed the effect of progesterone and 17 alpha-hydroxyprogesterone (17 alpha-OH-progesterone) at concentrations of 0.01-10 micrograms/ml, on the acrosome reaction and in vitro fertilizing ability of mouse epididymal spermatozoa. Cumulus masses containing oocytes were cultured in Brinster's medium, to which were added capacitated epididymal spermatozoa which had been incubated in medium with various concentrations of progesterone or 17 alpha-OH-progesterone for 90 min. IVF success rate was assessed 20-24 h following insemination. Progesterone was found to increase the fertilization rate at the 1 microgram/ml and 10 microgram/ml concentrations while lower concentrations had no effect. However, 17 alpha-OH-progesterone failed to show any effect on fertilizing ability. Incubation of epididymal spermatozoa in medium containing 1 microgram/ml and 10 micrograms/ml progesterone significantly increased the acrosome reaction as monitored by a chlortetracycline fluorescence assay. 17 alpha-OH-progesterone, however, failed to show any effect on the acrosome reaction. The results suggest direct effects of progesterone, but not of 17 alpha-OH-progesterone, on fertilization and the acrosome reaction of mouse spermatozoa.

17-alpha-Hydroxyprogesterone↗
PubMed1995

Plasma membrane block to polyspermy in human oocytes and preimplantation embryos.

The existence and time course of the human plasma membrane block to polyspermy were investigated by an in vitro fertilization assay using zona pellucida-free unfertilized oocytes, pronuclear oocytes and embryos. In the time course study using a high sperm concentration (10(5) spermatozoa ml-1), the number of penetrating spermatozoa at 30 and 60 min after insemination were 1.3 +/- 0.3 and 2.9 +/- 0.4, respectively. By 2 h after insemination, spermatozoa penetration reached a maximum. A lower maximum number of penetrating spermatozoa was observed at a low sperm concentration (10(4) spermatozoa ml-1), but the number of penetrating spermatozoa still reached a maximum by 2 h after insemination. A reinsemination experiment demonstrated that the number of penetrating spermatozoa was not significantly different between control and reinseminated oocytes, while sperm penetration was not observed in the oocyte beyond the two-cell stage. Furthermore, the number of binding spermatozoa decreased after fertilization and most of the four-cell stage embryos displayed no sperm binding. These results suggest that the plasma membrane block plays an important role in the prevention of polyspermy in the human oocyte, and that the plasma membrane block may involve permanent changes in the binding or fusion ability of spermatozoa in the oolemma after fertilization.

Blastocyst↗
PubMed1994

The effects of polybrominated biphenyls and perchlorinated terphenyls on in vitro fertilization in the mouse.

Polybrominated biphenyls (PBBs) and perchlorinated terphenyls (PCTs) are industrial chemicals that are long-lasting environmental contaminants. Although in vivo effects of PBBs on reproduction are documented, no information is available on the effects of these chemicals on sperm-egg interactions or fertilization. The present study was undertaken to determine the toxic potential of PBBs and PCTs on in vitro fertilization (IVF) in the mouse. 2-Bromobiphenyl, 4-bromobiphenyl, o-terphenyl, m-terphenyl, and p-terphenyl were added to the IVF medium at various concentrations. Oocytes collected from superovulated B6D2F1 mice were maintained in a medium containing the chemicals. Capacitated sperm were then added and the dishes cultured in a humidified atmosphere at 37 degrees C in 5% CO2 + 95% air. Oocytes were assessed for fertilization 20-24 h after insemination. polybrominated biphenyls and PCTs reduced the IVF rate at the higher dosages. Furthermore, an increased incidence of abnormal two-cell embryos and degenerative oocytes was observed at the 1 and 10 micrograms/ml concentrations of PBBs and PCTs. These results indicate that PBBs and PCTs adversely effect IVF and increase the incidence of abnormal embryos and oocyte degeneration in the mouse.

Animals↗
PubMed1992

Cellular toxicity of toluene on mouse gamete cells and preimplantation embryos.

Toluene is an aromatic hydrocarbon, which has been used in the paint, lacquer and glue industry. It has been detected in municipal water supplies. Previous mouse in vivo studies indicated that toluene administrated by gavage increased the embryonic mortality. The present in vitro study demonstrated that a concentration of toluene higher than 8.67 micrograms/ml not only decreased sperm motility and inhibited fertilization, but also significantly increased preimplantation embryo degeneration. At lower levels no effects were observed and the adverse effect levels were approximately 780 fold higher than reported levels in municipal water supplies.

Animals↗
PubMed1992

Toxicology of maternally ingested trichloroethylene (TCE) on embryonal and fetal development in mice and of TCE metabolites on in vitro fertilization.

Trichloroethylene (TCE), an industrial solvent, is a soil and ground water contaminant found across the United States. The metabolism and carcinogenic potential of TCE have been studied extensively in the past 15 years yet there is little information on the chemical's possible effects on reproduction. No reference to the reproductive effects in mice of TCE by oral administration exists in the literature. In this study, female B6D2F1 mice were gavaged from Days 1 to 5, 6 to 10, or 11 to 15 (Day 1 = vaginal plug) with TCE in corn oil at 0, 1/10, and 1/100 of the oral LD50. Weights of mice were recorded and the livers and kidneys were weighed and preserved in 10% buffered formalin. Litters were counted, sexed, weighed, and measured for crown-rump length until weaning on Day 21 and some animals were allowed to develop to 6 weeks of age. At this time, a minimum of two litters from each dose were killed and gonads removed, weighed, and preserved in Bouin's fixative. Litters were also assessed for developmental abnormalities. No maternal or reproductive effect of TCE was seen at either dose level. TCE, administered consecutively on Days 1 to 5, 6 to 10, and 11 to 15 of pregnancy, does not appear to be a potential reproductive toxicant up to 1/10 the oral LD50. In a second series of studies, TCE and its metabolites dichloroacetic acid (DCA), trichloroacetic acid (TCAA), and trichloroethanol (TCOH) were added to culture media to assess the toxic effects on in vitro fertilization (IVF) in mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Microencapsulation of single, multiple, and zona pellucida-free mouse preimplantation embryos in sodium alginate and their development in vitro.

Preimplantation embryos obtained from immature superovulated B6D2F1 female mice were microencapsulated in sodium alginate singly, in multiples of 2 or 3, or denuded of their zona pellucida. Encapsulated embryos developed in vitro at a rate similar to control embryos. Development of zona pellucida-free embryos was significantly less than that of intact embryos, but there was no difference between encapsulated and non-encapsulated zona pellucida-free embryos. Development of 2- and 4-cell embryos in sodium alginate was independent of cell stage. This report demonstrates the usefulness of a viable, biodegradable embedding material for the microencapsulation of manipulated preimplantation mammalian embryos.

Alginates↗
PubMed1990

In vitro fertilization in nonhuman primates.

Ovulation induction, sperm capacitation, and fertilization have been studied for over 50 years in nonhuman primates but it has only been in the past 20 years that extensive studies on sizeable numbers of embryos have been carried out. Of over 200 species of nonhuman primates only a few have been studied and the majority of the findings come from studies of the squirrel monkey, baboon, rhesus, and cynomolgus macaque. Nevertheless, the fertilization process appears to be similar to that identified in other mammals and in man.

Animals↗